MANILA—In what is expected to mark a pivotal moment in this rapidly developing but still impoverished nation, the Supreme Court of the Philippines will next month weigh the constitutionality of a new reproductive health law that pits the entrenched power of the Roman Catholic establishment against a rising tide of modernization and economic aspiration.

The measure, which was signed into law last December after a bitter 14-year battle between women’s rights advocates and Catholic bishops, would fund access to contraceptives for the nation’s poorest women. The key question before the court is whether it violates a 1987 constitutional guarantee of protection for “the life of the unborn from conception.”

Catholic bishops in this profoundly Catholic country of 96 million argue that any form of contraception other than Vatican-approved “natural” methods or abstinence is tantamount to abortion. They also warn that the RH bill, as it is called here, is the first step down a slippery slope that will inevitably lead to the legalization of abortion, euthanasia, divorce, and same sex marriage.

The law has been backed by a loose alliance of women’s groups, medical professionals, academics, business leaders, celebrities and a few progressive Catholic organizations. It also received key support from President Benigno Aquino III, who ignored threats of excommunication to actively campaign for its approval.

Archbishop Ramon Arguelles, a vice-chairman of the Catholic Bishops’ Conference of the Philippines, said that Aquino’s support for the RH bill was a declaration of “open war” on the church.

It is not a war the bishops intend to lose. Long accustomed to a position of unquestioned power and privilege in the Philippines, the church hierarchy fears that its moral authority is eroding in the face of dynamic economic growth—the Philippines has just replaced China as the fastest growing economy in the region—coupled with the deepening frustration of the many millions who remain mired in poverty.

“For the Catholic Church here and for the Vatican, this is a real struggle. This is a country they don’t want to lose. We are the last bastion of Catholicism in the Old World colonies,” said Sylvia Estrada-Claudio, director of the University of the Philippines Center for Women’s Studies and a longtime activist for reproductive health.

In December, when the bill came to a vote, bishops and nuns packed the public galleries of the Philippine Congress. Their presence seemed calculated to intimidate, but they ended up watching in stunned silence as lawmakers approved the measure. The vote was 13 to 8 in Senate and 133 to 79 in the House of Representatives. A week later, Aquino signed the bill into law.

“This is the first time we quote-unquote ‘lost’ on this issue,” said Father Francis Lucas, a spokesman for the bishops’ conference. “We may have lost a battle, but we haven’t lost the war.”

To rally support to its side, the bishops attempted to turn last month’s mid-term elections into a referendum on the law. Labeling the church and its supporters as “Team Life” and their opponents as “Team Death,” bishops and priests across the Philippines used their Sunday pulpits to call for the defeat of candidates who had voted in favor of the bill.

The church was hoping for a crushing victory, but each side managed to get about half its candidates elected, a result that was widely interpreted as a setback for the bishops and “Team Life.”

Both sides are now gearing up for next month’s Supreme Court showdown.

The bishops’ conference has been openly lobbying some of the Supreme Court’s 15 justices, 11 of whom were appointed by Aquino’s predecessor, Gloria Macapagal-Arroyo, a staunch supporter of the church’s position on contraception.

“We could lose it. We’re hopeful that we won’t, but we are not sure,” said Estrada-Claudio, the reproductive health activist.

Elizabeth Pangalangan, a Harvard-trained lawyer and professor at the University of the Philippines Law Center who will be arguing in favor of the bill, said the biggest issue is whether the law violates the right to life protection in the constitution.

“What is prevented by the constitution is abortion,” she said. “To win we will have to stress the fact that we are against abortion.”

In addition to providing modern contraceptives to poor women, the law also mandates sex education in public schools and requires hospitals to provide post-abortion care—yet another sensitive subject in the Philippines.

Despite the blanket ban on abortion, it is estimated that some 475,000 to 600,000 women undergo illegal and often unsafe abortions each year, and that about 90,000 of these women are later hospitalized for post-abortion complications. About 1,000 women die each year from botched abortions, according to a study by the Guttmacher Institute, a New York think tank that supports access to contraceptives and legal abortion.

The Philippines has one of the highest birthrates in Southeast Asia, and surveys indicate that 54 percent of the pregnancies that occur each year are unintended or unwanted. The vast majority of those pregnancies occur among poor women with little or no access to modern contraceptives.

Supporters of the law argue that providing poor families better access to contraceptives would substantially lower the birthrate and also reduce the number of abortions. The church, in addition to its objections on theological grounds, contends that easy access to contraceptives would only lead to promiscuity among the young.